1. Field of the Invention
This invention relates to recording apparatuses used with flexible media and, more particularly, to a magnetic head slider and a support mechanism therefor, used for flexible magnetic disk apparatuses, electronic still image recording apparatuses, video tape recorders, etc.
2. Description of the Prior Art
Up to date, a flexible magnetic disk apparatus disclosed in Japanese Patent Publication No. 58-15866 has been widely used. The construction and operation of this apparatus will be described with reference to a plan view of FIG. 9 and a partly sectional side view of FIG. 10. Referring to these Figures, designated at 1 is a magnetic disk, and at 20 a carrier. A stationary converter 21 of a well-known button head type is mounted on carrier 20 at a free end thereof. The converter 21 is set such that it slightly wedges into a principal surface of disk 1. Canti-lever type load arm 22, which has small mass and comparatively high mechanical strength, is pivoted to the end of carrier 20 remote from converter 21. It has a small hole formed near its free end, and magnetic slider 23 is provided in the hole. Magnetic head slider 23 is attached to an end of a short two-axis gimbal spring 24. It has a bottom attached to and extending along arm 22 and radially spaced apart from the magnetic head slider Designated at 25 is a pivot extending from a position of arm 22 near the free end thereof and through the hole to keep a central portion of magnetic head slider 23. Control knob 26 is provided on arm 22 near the free end thereof. It can be engaged with a solenoid operation member (not shown) for rotating arm 22 in directions for engaging and disengaging the magnetic head with and from magnetic disk 1. Arm 22 has its lower end connected by the agency of light leaf spring 27 to an end of carrier 20. The rotation noted above is caused by this spring. Spring 27 engages in a position with head stopper 28 to restrict motion of the head toward stationary converter 21. Nar an end of a rotational shaft of arm 22, cylindrical core member 29 is connected to carrier 20. Torsion spring 30 is wound on the core member and has a straight end portion extending along the body of arm 22 to exert a spring load to arm 22 toward stationary converter 21.
In operation, when recording or reproducing data, the solenoid operation mechanism (not shown) engaging with control knob 26 on arm 22 is energized to let torsion spring 30 urge magnetic head slider 23 against the surface of magnetic disk 1. Magnetic disk 1 thus is sandwiched between stationary converter 21 and magnetic head slider 23 in contact with these parts. Stationary converter 21 and surface of magnetic head slider 23 are held substantially parallel by a force of about 14 gr. applied to magnetic head slider 23 by torsion spring 27 or 30. When magnetic disk 1 is sandwiched between stationary converter 21 and magnetic head slider 23, the initial sagging of disk 1 is corrected, and thus stable state of contact can be maintained.
This structure, however, has the following deficiencies.
(i) With an air bearing effect provided by entry of air into the space between the magnetic disk and magnetic head with rotation of the magnetic disk, the pressure of air in the space between the magnetic disk and head slider becomes higher than atmospheric pressure (i.e., becomes positive) during operation. A gap is thus liable to be produced. Therefore, it is necessary to increase the force of the torsion spring applied to the magnetic head. PA1 (ii) At the time of the start of the magnetic disk, this force entirely constitutes the pressure contact with the disk, and the disk is thus liable to be damaged. In addition, at the time of the start great frictional force is produced to increase power consumption. PA1 (iii) The pressure of contact between the disk and head is determined by the equilibrium between the force applied by the torsion spring and air pressure provided by the effect of air bearing. This equilibrium is changed instantaneously by initial deformation and posture of the disk and external disturbances such as vibrations of the disk. The contact pressure distribution, therefore, can be difficultly stabilized and changed greatly during operation. PA1 (i) Since the magnetic head is supported in projected state in the recessed portions, the control of extent of projection is very difficult. In addition, the contact areas of the magnetic head and medium are very small while the contact pressure is comparatively high, the magnetic head is readily worn out. Therefore, the extent of projection is variable, and the life of the head is short. PA1 (ii) The contact pressure is liable to cause damage to the magnetic disk. In addition, the magnetic disk undergoes comparatively large local deformation in the neighborhood of the magnetic head, and repetition fatigue thus readily takes place. For this reason, data omission or the like is liable to be increased to deteriorate performance concerning reliability which is important for the recording and reproducing apparatus. PA1 (iii) Since the head and disk are brought into contact with each other with deformation of the disk caused by the negative pressure effect, it is essentially difficult to make recording and reproduction on both sides of the disk. This is so because if a magnetic head support is provided on each side of magnetic disk, negative pressures generated on both sides of the disk cancel each other, making it difficult to obtain deformation of the disk in conformity to the radius of curvature of gap formation section 42a.
In other words, the stability of contact between the magnetic disk and magnetic head slider is low, and therefore high local contact pressure is liable to be produced in the contact section to reduce the reproduction output from the magnetic disk (or result in reduction of magnetization due to pressure application) and, in a worst case, cause damage to the disk.
A different example of the apparatus of this type is disclosed in Japanese Patent Disclosure No. 1-94563, and it is widely used in the field of electronic still image recording apparatuses. To overcome the above drawback, the above apparatus is provided with a head support such that the air pressure in the neighborhood of the magnetic head is lower than atmospheric pressure (i.e., negative) as a method of supporting the head. The construction and operation of the apparatus will now be described. FIG. 11 is a sectional view showing the apparatus, FIG. 12 is a plan view showing the same, and FIG. 13 is a sectional view for explaining the operation. Referring to the Figures, designated at 41 is a magnetic head support, and at 42 a magnetic head supported by magnetic head support 41. Magnetic head support 41 has first annular projection 41a and second projection 41d defining inner mounting hole 41c and serving as negative pressure generation means. First recessed portion 41b is formed between first and second projections 41a and 41d, and small second recessed portion 41e is formed between gap formation portion 42a of magnetic head 42 and second projection 41d. Gap formation portion 42a of magnetic head 42 is upwardly inserted in mounting hole 41c and secured in position projected slightly from the top surface of second projection 41d.
In operation, as shown in FIG. 13, as magnetic disk 1 is rotated at high speed in the direction of arrow A, negative pressure is produced in first and second recessed portions 41b and 41e. The disk is thus sucked against the top of magnetic head support 41 and deformed after the recessed and projected shape of magnetic head support 41. With positional relation between first projection 41a and first recessed portion 41b negative pressure is produced in first recessed portion 41b after the Bernoulli Law, and magnetic disk 1 is led to gap formation section 42a of magnetic head 42 with its height determined by second projection 41d. Thus, in gap formation section 42a magnetic disk 1 is deformed along the radius of curvature of gap formation section 42a, and magnetic head 42 thus can be in stable contact with magnetic disk 1.
However, the above structure has the following drawbacks.
As shown above, with the prior art apparatus of the positive pressure type structure, in which magnetic disk and head slider are brought into contact with each other by urging the disk, a pressure for urging the magnetic head against the magnetic disk is necessary. At the time of the start, this pressure constitutes a contact pressure on the disk and is liable to cause damage to the disk. In addition, the contact between the magnetic disk and magnetic head slider is poorly stable, thus leading to reduction of the reproduction output and, in a worst case, causing damage to the disk. With the prior art apparatus of the negative pressure type, in which the magnetic disk is sucked, the disk undergoes comparatively large local deformation in the neighborhood of the magnetic head, and repetition fatigue thus readily takes place, leading to reduction of the reliability and also to such problem as impossibility of recording and reproduction on both sides of the disk.